The practice of modern medical technology has adopted the usage of a standard device or method for the collection of blood samples from patients. Although the blood collection devices may be made by a number of different companies, they share the same basic characteristics. The typical unit comprises a tubular holder, preferably of plastic construction, wherein one end terminates in a tapered projection known as a needle mount. The other end has an opening of a size that is compatible with the receipt of the tubes used in the blood collecting process.
Specifically, the needle mount is made to receive a double ended needle assembly that has a hub disposed about the central portion of the needle. The hub is compatibly sized to mate with the end of needle mount and be retained thereon. Once assembled in this manner, one end of the double ended needle extends inwardly into the holder and the opposite end of the needle extends outwardly from the hub.
A number of different needle fittings are known. These differ primarily by the methods in which they connect to the needle mount. For example, one method is a threaded engagement of the needle fitting to the needle mount. Another is known as a bayonet style, in which both components have spaced flanging that allows the insertion of the needle fitting into a needle mount, and after a partial turn, the needle fitting is connectibly retained to the mount.
Another type of needle fitting commonly employed on syringes is known as a Luer fitting, which comprises a hub with an internal diameter sized for compatible installation over the outer diameter of the needle mount. The fit is tight enough to cause the hub to be retained on the mount and is overcome by twisting the installed parts in order to release the hub from the mount.
Once the collector is assembled with a needle assembly, the usual practice is to insert the needle extending from the collection holder into the patient whose blood is going to be drawn. At the same time, a specially prepared tube is positioned into the opening at the other end of the holder. One end of the tube is closed, and the other end is provided with a puncturable seal that protects the contents of the tube from contamination from the outside environment. The interior of the tube is placed under a slight vacuum. The tube with the sealed end is inserted first and is pushed through the holder until it contacts the inwardly projecting portion of the needle assembly. At the appropriate time, the seal end is punctured by the needle and the vacuum is exposed to the bore of the needle and exerts an extraction force causing blood to be collected into the tube. Once the sample volume has been obtained the tube is withdrawn from the holder, and the holder is withdrawn from the patient. The seal on the tube returns to its sealed state and preserves the integrity of the sample thus drawn. At this point, the tube may be sent for processing.
The holder is designed to be reused while the needle assembly is removed and discarded. One means for removing the needle assembly is a plastic sheath that fits over the outwardly extending portion of the needle assembly and compatibly grips the needle fitting, thereby removing it from the needle mount. In order for the holder to be reused, the above procedure is repeated.
One problem that has been associated with the use of this blood collecting device has been for the tendency of the medical technician to slip while trying to enclose the needle with the plastic sheath after taking a blood sample. This may result at times in the medical technician being punctured by the needle and potentially exposed to the blood of the patient. Of grave concern is the transmission of disease such as hepatitis or AIDS (Acquired Immune Deficiency Syndrome) known to be communicable by such mishaps.
Another problem associated with the standard blood collection assembly is the weakness that develops in the fit between the needle mount and the needle fitting such that separation during the blood sampling process may lead to incomplete collection of the sample, contamination of the sample, and on occasion the separation of the needle fitting from the blood collecting holder with the embarrassing and potentially dangerous situation where the needle assembly remains in the patient.